Method and apparatus for draft control



July 10, 1945. R. R. M IN' IOSH 2,379,916

1 A METHOD AND APPARATUS FOR DRAFT CONTROL Filed March 1, l94l 4 Sheets-Sheet l "l-Tcl j INVENTOR Y rt Rjglgw ATTORNEY 'F Tc -L Robe 4 s'ne'ets-shet 2 .4 I I I I I I I 'l I I I 1- .II I

ON R July 10, 1945.

R. R. MclNTOSI-l METHOD AND APPARATUS FOR DRAFT CONTROL Filed March 1, 1941 July 10, 1945.

R. R. M INTOSH METHOD AND APPARATUS FOR DRAFT CONTROL Filed March 1, 1941 4 Sheets-Sheet 3 ATTORNEY of the locomotive.

Patented July 10, 1945 UNITED STATES PATENT, -oFFlor. A A

Ms'ruon AND APPARATUS FOR DRAFT CONTROL Robert McIntosh, ne: aemon; Application March 1, 941, sesame 381,290 r 13Claims. (o1. 110150) The present invention relates broadly to :the automatic regulation of draft for the hot DIOd-r grates is often resortedito as a Supplemental means .of draft fluctuation" control, andthis again ucts of combustion used in generating steam'and 1 the like, and in its specific phases it relates to 1 methods and apparatus for usein automatically controlling the induced draft created in railway locomotive smoke boxes. v

The standard practice for creating draft in railway locomotives is to use the exhaust from the driving cylinders to create a partial vacuum in the smoke box atthe front end of the locomotive, and to supplement'this with alive steam blowcr' for useduring standing and drifting operation of the locomotive. Draft produced in ,this manner varies with the per cent cut off at suction pressures which, at the higher suction pressures, carries small cylinders and burning coalparticles from the fire box and blows them utof the smoke stack, a thing which not, only "requires'further increase of the back pressures on the cylinders with the detrimental. effect noted. Attemptedsolutionsof this nature take into consideration the fundamental need of artificial draft; but fail, to do more than lower :and

imposed by the baffles or reduced grate, opening a it area and yet maintain sufiicient "draft for ,com-

bustion in" the fire box. It was with ayrviewto thesolution of theseproblems that a study of creates a dirt nuisance, fuel loss, and a fire hazard, but abrasively wears out the tubes, superf heater units, and front end surfacesexposed to the flow; of gases. containing these particles. This practice also results in, dilution of the products of combustion with excess air, andwastes heat dueto toorapid flow of the diluted products 1 l of combustion from the fire box to the front end In an effort to partiallyred uce the detrimental effect of, excessive and fluctuating suction in the smoke box the practice has grown up tinstalling baffle plates to restrict the flow areas in an attempt to control the flow of products of combustion through the smoke box, and such baffles are further supplementalwith a netting to hold back and break with; larger cindrs and burning pieces of; fuel drawn outof the fire box 4 due to such suction. Th practice. of bafiling is of some beneficial aid in holding the suction pressures within closer limits but this still leaves undesirable fluctuations .of same, and requires higher suction pressures in front of the baffles to overcome the effectl ofthe restrictions The production of these higher suction pressures in turn requireslth employment ofhigher steam I exhaust backfpressures from the cylinders, a

thing which. reduces the output of the 000mm tive. Higher suction also automatically requires a higher'firing rate to utilize the excess air and reduce its cooling effect upon the heating surfaces, thus increasing fuel consumption. Bestricting the area of the openings through the amount.

the locomotive drafting situation was made which resulted in the present discovery that fluctuations in suction pressures could be held much closer within predetermined limits without restricting the free flow o'fthegases in thelocomotive front end'or reducing the grate'opening areas. This permits the air drawn throughthe fire box, tubes, and smoke box to flow freely and be in relatively proper amount forsatisfactory combustion fficiency with substantial: elimination of excessive'dilution'with its cooling effect on 'the products of c'ombustionqflowing to the smokebox. The freeing and equalizing of the gas'flow areas throughout the systemeli-minates I the necessity for increased exhaustback pressure made possibl by freeing the gas flow, areas is of fpositiveaid in increasing the locomotive Ieiilciency andoutput. The methodsand apparatus involved inthe accomplishinglof these ends forms the basis of the present invention. ,1 u Accordingly, among the objects of the present invention is the provision of a method and ap paratus for automatically conrtolling the suction pressures utilized in producing induced draft between predetermined limits. l q

Another objectis to provide an apparatus which prevents suction pressures in excess of a prescribed limit. I l

Another objectis to provide smoke box in amount sufficientfto prevent the bustion therein 'from exceeding a prescribed Another object is to provide a damper system a damper system which automatically allows air to enter the as to permit a controlled flow of hot products of combustion through the superheater portion of the boiler, thus raising or lowerin'g, as desi'red,-the superheat temperature of the steam produced, with resultant increase in the Rankin .cycle effi- Figure 5 is a partially sectioned elevational View taken along the line 55 of Figure 4 looking in the direction of the arrows.

Figure 6 is .a sectional view through a modified form of automatic air inlet valve assembly. Figure 7 is a sectional view through'another form of automatic air inlet valve assembly.

Figure -8 is an enlarged fragmentary sectional view showing a preferred form of inlet valve seal-f in'gmeans. 1 I

Figure 9is aside elevational view of a preferred form of louvres and operating mechanism as viewed from the right side of Figure'S.

ciency and decrease in the amount of steam re-' quired when this temperature is above that previously attained with the conventionalrdesign.

A still further object is to not only reduce dilution with its cooling effect onlthe products of combustion in .the fire box but :also to reduce their velocity in contact with the heating :surfaces so as :to permittimefor grea'terheat transfer, while preventing the carriage of excess amounts of abrasive material and burning solid fuel past the heating surfaces, thus reducing the firing rate ofthe combustible 'to a point conforming with th actual requirements of the engine.

A still further object is to produce amethod and apparatus 'for the automatic controlling, and balancing of the smoke box draft within limits I deslred'for minimum and maximum demands for air 'required for combustion.

A still Turthergobject involves the .use of means for delivering the controlled suction :pressure reducingair directlyto thebase of thesmoke stack,

thus avoiding anystresses and strains in or on the ,front end of the-locomotive due to variations in temperature within the smoke box occasioned .by the-admission ofsuch air.

still further objects and-advantages of the present invention will appear as the description proceeds. r

assemblies.

Figure 10 is 'a'partially sectioned top view of a "major portion of the apparatus shown in Figure 9. with-certain parts of the air inlet valve assem bly shown in detail.

Figure 11. is a top view of a modified form of thelouvre operating assembly of Figures 9 and 10. Figure 12 is a front elevational view of the louvre operating assembly shown in Figure 11.

Figure 13 :shows in diagrammatic manner a convenient means .of connecting the fuel valve of an oil fired locomotive .to the steam valve I which control the .louvres on; oneof the air-inlet Referring more particularly I through which-asmo-ke stackrz projects-inconventional manner. The lower end of the smoke stack .is normally provided with a removable .de-

' pending-extension 3 having a flared bottom por- .tion :4 commonly called .a petticoat.

To the accomplishment of the foregoing and related ends, the'inventiongthen consists of the steps and means hereinafter fully described and particularly pointed out in the claims, the annexed drawings and the following description setting forth in detail certain means and modes of carrying ,out' the invention, such disclosed means and modes illustrating, however, but several 0f the various ways in-which the principle of the invention maybe used.

In'saidsann'exeddrawings: Figure 1 is "a sectional front elevation through the front endof :a conventional locomotivesmoke box, at .a point idirectly in front of the smoke stack, showing in diagrammatic manner a sim- =plified assemblyof one form of the present in vention. I 1

Figure 2 is'asideelevationaofla locomotive front end with part of thesmoke-boxshell removed to illustrate an installation having a modified form "of the construction. H n T *FigureB is a perspective view of a locomotive front end'with the shell diagrammatically shown and partially broken away to reveal the mechanismtillus-tratedzin Figure 2, certainor the parts being :omitted for purposes of: clarity.

Figure 4 is a side elevation of a locomotive frontend withpart of the smoke box shell broken away to show a modification of the construction illustrated in Figure 2. r

below the smoke stackuextension is an exhaust stand 5 .havingwa nozzle .6 ,for directing exhaust steam from the locomotive driving cylinder-s (not shown) up the smoke stack in conventional unanner forming a seal .therewithso as to produce a partial vacuum in thelocomotive front-end which is commonly termed the :smoke box. In order to induce some draft when the locomotive isstandingstill, .orusing. little driving .steam, a blower ring I is mounted at the upperend-of andaround theexhaust stand nozzle. This ring is connected l by -means of pipe .8 :tothe livef'steam gen'erated inthe boiler. A suitable valve (notshown) .enables the fireman to .controlthe delivery of live steam to ring 1 which is suitably perforated .to deliver .steamup the'smoke stack and thus create a moderate inducedv draft' In the standard A. A. R. (Association of American Railroads) .front end construction the-smoke box is provided witha diaphragm 9 (Figures land ,2), table platel ll baffle plate H, and netting .12. The usetof baffle. plate 4| permits choking the area for flow of products of combustion so that it i smaller than theffree area of the fire tubes through which the: smoke fiows from the firebox -(not shown) to the smoke box. In this manner the suction pressure range back .of the diaphragm .9

is lower than that behind screen l2.and infront of diaphragm 9. In accordance with one phase ,of .the present invention .the passageway for smoke .through the smoke .box to the smoke stack is increased in size untilit is largeorlarger than,

the total free area through the fire tubes thus making possible substantial equalization of the suction pressures in frontof and back of the dia- V phragm. This can be substantially effected by removing baffle plate 1 I, although the invention is not limited to that specific'alteration. One

or more air inlet assemblies I3 and-M may then be installedin front of diaphragm 9 or at some other point subject to high suction pressures, and such assemblies individually adjusted toad,-

to Figure rer the drawings, the locomotive front .end' has a shell Directly upper suction pressure ispreferably determined bytests or computation so as to limit the maximum amountof air drawn through'the fire box to that which will efflciently burn all of the fuel required to meet the maximum steam demand.

procedureprevents excessive dilution and cooling ofthe products of combustion, reduces the carriage oi cinders and burning fuel particlesout through the smoke stack,and; improvesthe efiiciency. of heat absorption by reducing the maximum rate of travel of {the products of combustion past the heat absorbing surfaces. i A preferred form of air inlet assembly I3 consists of a housing! 5 (Figure 5) open at both ends and provided with afvalve seat ring l6 having'a suitable gasket 11 (Figure 8') against which disc valve]; sealswhen in closed position. Typical of gasket material usable asshown in Garlock} wherein a'gisc valve la is pivotallymounted on hinge32 and provided with "an eye bolt 33 to which a cable 25a.maybe attached. This cable a:suitable 1 opening in cover disc 34. and has weights of. suitable size and amount mounted thereon in conventional manner. A valve seat ring 16a with gasketll thereon cooperates with disc valve [8a to form a seal therewith at all times when the suction pressure acting on disc valve woven asbestos packing which is cemented. driven into place, and its projecting faoe leveled. .S oft metal with a suitable high melting point, prefer ably over 600 F, may be driven into place and faced, and one such material is annealed copperi For convenience of assembly and operation, disc valve 18 is radially mounted in fixed position on shaft l9 which is supported and endwise movable through suitable bearings in outer and inner supporting members 20 and 2|. The bearings in these supporting members may be of various types of construction and to typically illustrate same the outer supporting member 20 is shown as having a typical stationary slide fit bearin'g'22, while the inner supporting member 2| is provided with a movablebearing in the form of a pairof grooved pulley sheaves 23. In order to hold the valve in closed position until a predetermined maximnm.

suction pressure within the smokebox has been reached, suitable weights 24 of required size and quantity may be utilized, and these in turn are connected to disc valve l8 by means of cables 25 passing over suitable pulley sheaves 26. Forcom venience of operation these pulley sheaves may bemountedon horizontal shaft 21, In order to protect and stabilize the weights 24 while avoiding leakage of air past same into the smokebox. a suitable housing 28 closed at its lower end and joined to the smoke box shell I by means ofan anchorin member 29 may be used. A convenient means of joining weights 24 to a pair of disc valve operating cables 25 involves the use of a T-shaped member 30 mounted as shown. The invention. however, is not limited to that specific assembly andtheshowing of same is to be considered as diagrammatic of the various equivalent constructions of this type. For convenience of joining the valve assembly housing 15 to smoke box shell I in manner permitting ingress of air through the valve when open, a tubular member 31 of suitable construction and size may be used. One

convenient form of this consists of the flanged member shown which is adapted to be welded in air tight manner to shell. 1, as well asbolted or otherwise conventionally fastened to housing 15 so as to permit disassembly and removalof the latter when repairs are to be made which necessitate such removal. The general combina tion of air inlet assembly [3 with shell I as thus described, is typically shown in preferredloca' ti0n;in Figure 1, and various details of same are. illustrated in Figures 4 and 5.

. i A modified construction of the air inlet valve.

in partially open position, is shown in Figure 6 l8a doeshot exceedfthe predetermined suction pressure which weights; 24 are adapted to counterbalance; With this type of construction thevalve assembly may be built directly into tubular anchoring member 29a which is joined in fixed position to shell .I. If it is desiredto connect this valve assembly to some localized point of application of suction pressure reducingeffect a suitable tubular member35 may be utilized this memberto facilitate disassembly of the systemis preferably provided with a flange 36 adapted to bejoined to flange 31 of anchoring member ZSa by means of bolts 38 or the equivalent, Another modified form of air inlet assemblyis shown in Figure '7. In the place of weights this construction utilizes a compression spring 39 to hold disc valve 18b in closedposition, andfyet allow same to open as shownwhen the suction pressure effect thereon exceeds the closing presincreasing quantitiesof air. v

tained through the increasing resistanceof the sure exertedby spring 39. The valve may; be easily adjusted for opening at a predetermined suction pressure by threading the outer end of shaft l9aand providing same with a nutBB and look nut 8'! for adjusting the spring compression pressure to thedesired point.. Theme of a Spring controlled inlet valve permits startingthe adfmission of suction reducing air to the smoke-box at a predetermined suction pressureandyet per mitsthesuction pressure to raise appreciably the further disc valve [to is moved inward to admit spring as it is progressively compressed. Under these conditions with a locomotive operating under heavy load near its maximum pulling capacityand atgrelatively high suctionpressure generation, this spring balanced valve can beso proportioned as to allow the upper suction pres- .suretobe maintained at aslightly higher level.

thus increasing the draft and facilitating increased steamgeneration'. The housing libin this case would be provided with valve seat ring l6 for use as previously described. The shaft [9a, if desired, may be supported at both ends as :Deak fuelfeed conditions. The assembly- M on i the other hand may be set to open at a predetershownjin connection with shaft 19 in Figure 5, but for simplicity of construction the apparatus has becnflillustrated in Figure 7 as utilizing a single stationary slide fit bearing .22

. carried by an outer supporting memberzlla. 1

The maximum suction pressure to be applied in the smoke box at the point ofadmission of smoke thereinto' is preferably controlled so asto prevent with a pair of air inlet assemblies l3 and II. The

assembly l3 for instance being set forthe admission of air to restrict thesuction pressures in. the smoke. box to a predetermined maximum suitable for high combustion eiiiciency under substantially This sheet is ob mined lowersuctionpressure in the smoke .box

thus takingscare .of the maximumsuction presthenv it'isdesirable toraise the suction pressure in the smoke box so asto permit the maximum suction pressureto be increased to the limit :for

which air inlet assembly l3 has been set. To.

accomplish this the flow of air through .air inlet assembly [4 may be automatically stopped when the rateof fuel-feed. exceeds ,a predetermined amount, and a convenient meansfor accomplish,- ing this will now be described.

Referringto Figures v9 and i" thelair inlet as sembly l4 isprovided with a tubular. member lfl having louvres 4 l and 42 pivotallymountedthere;

in and adapted to substantially prevent the pas,-

sage of air through tubularmember do when said louvres are-moved .to closed position. For clarity of illustration these louvres are shown in partially opened position. Fixedlymounted on flth e upper end of shafts 53 and A4, which :have louvres 4! and 42:.respectively anchored thereto, are a pair of slotted lever arms .45 and =46. Mounted above these'slotted leverarms is an endwise movable rod 41 supportedby suitablebearings in extend.- I

ingj armmembers 48..and 49. Rod .41 in this construction is provided with conventional meansfor preventing rotationof same, ajthing which may be easily: accomplished, for instance, by keying or feather keying the shaft anda corresponding hearing, or by making a .portionof the rod square and. the bearing through which .it slidesof like cross section for av free sliding fit. therewith throughout the full travel of the rod. The show.-

ing. in Figures .9 and 10 is intended to diagrammatically illustrate this general typeof construc tion. it Mounted on the under faceofrod 4'! in position to operativelycooperatewith the/slots in slotted lever arms 45 and .46.are a pair of slot engaging members 50 (and 5|. Mounted on one end of rod 41 is'a compression spring 52 adapted to normally ,hold the. louvres infull open position.

Nut 89 and lock-nut 90 threadedlyengage rod 4! and provide variations of the compression of spring 52 to take care of the adjustment oflthe louvre operating steam pressures to meet the particular requirements involved for openingand closingthe louvres at the chosen fuel feed rate, or the like, Apiston 53 is joined to the other end-of rod 41 and slidablyfits a cylinder .54

mounted onextending arm member 49. A pipe 55;connects the outer end of cylinder 54 toa suit:-

able sourrce of fluid-pressure such that when the fluid pressure delivered through pipe 55 into cylinder 54 exerts sufiic ient pressure. on piston. 53

to overcome the compression. resistance of spring 52, the piston will move to the left, and through the-agency of the members connected to. the louvres 4i and 42, willclose same. Where allowmotive is stoker fired, therateof fuelfeed tothe at which the apparatus has beenadjusted. This permits air inlet assembly 14 to be adjusted to maintain a maximum suction pressure limit, lower than that of .air inlet assembly I3, suited to conditions .ofllow. fuel feed operation wherein a mod.-

we draft w s pl -e the m nemi proper .combusi ion oi the fuel being fed into the ther flow off air, into the. locomotive smo'kje "box through,.ai;r inletlass einblyjl l. Air inlet assembly 1.3 wich isadaptje'd to limit the "maximum suction pressure irith'e smoke box to. that hi her sucftion" pressun "which has been. determined ,to. be SatisIactOryQMIIdia-ITZ conditions .of maximum. fuel consumption will then become effective, in. con.- trolling the uppersiictiori limit. AssemblyJ 3then maintains controllof .the maximum suction pressure inthe smoke box'nntil .suchthneas the iced is again reduced to a point where the .stea npressure on the stoker engine, through connection.l to. cylinder 54, allows piston 5.3 to ,move -.loackto the-right .underinfluence-of spring 52. This automatically opens louvresA'Land 42so'that air inlet assembly, l4 once more :controls the maximum suction pressure'at the .1ower'. .suction pressure level. A trap-Elie .usedto conventionall'ylwithe draw condensed steam ,froin the louvre operating steamsystem. I In 011181130 makeit possible for the fireman .to increase the maximum suction pres.-

sure limit evenunder lowfiririg rates, a .yalve58 louvres,.-compressed air may be used inequivalent manner. The invention I is not limited. toflthe use of one or two airinlet assemblies with alouvre assembly on alower pressureinlet assembly, but

rather a plurality of. such assemblies may be ued to step. 'up..the,. suction pressure as required and the showing. in, the drawings. is, intended to diagrammatically illustrate .sar'nel v Where the. present invention isused onan oil fired locomotive' the, fuel oil .fe ed valve (Figure "13.). ,may .be connected by means of lever 59,a to

valve 58 so that the, two valves will operate. in .unisonwhen oil fee'djlevergii lis operated, thus again makinglpossible the controlof the maximum suction pressure level in accordance with rate of fuel feed. f-. f A modifiedconstruction of thelouvre operating mechanism is shown inFigures 11 and v 12. In this construction shafts 33. and 44,,t0 which louvres 4i. and 42 respectively .are joined, have extending arms .6! and 62.mounted thereon andlco ected by a tying link .63 so that the-two louvres operate in unisonl. Extendingarm iii carr s an eXten;-'

sion 64 slidablyfitting-the .bore mofa sli'dable member- 65.which in..turn' isv connected to rod 4111 by means of a pivot member .65. Cylinder 54a and piston 53a in this construction are ar, ranged fordouble action operation. ,Steam. is delivered to the cylinder through pipe 55 as previously described while pipe jfiT islco nnected tofa a suitable steam trap or the equivalent-the former being illustrated'in .FigureQ. Livesteamis. used in this assembly to return louvres 4i and 42 to open position when the steam delivered through pipe 55drops below a predetermined point. The

louvre opening steam system operates on live steam, normally at boiler pressure, delivered through pipe 68 to pressure reducing valve 69 theoutlet of which is connected by means of pipe the smaller .tubessBLand the larger tubes 82 in which the superheater unit tubes 83 are placed. It is thus to be noted that by controlling the proportionate flow of hot products at combustion through the small and large fire tubes, the amount to the cylinder at the end of same opposite to the end connected to pipe 55. The steam pressure in pipe 10 is preferably controlled through pressurereducing valve 69 so that louvres 4| and 42 will openand close when therate of fuel feed goes below or above a predetermined amount. Pipe H connects the cylinder to a suitable trapor the equivalent (not shown) for draining c0ndensate from the lower edge of the cylinder at the endconnected by pipe 10. In order to relieve the pressure in pipe 10 when same exceeds the pressure delivered by pressure reducing valve 69, a small relief valve 12 is preferably connected to pipe III. This type of construction permits venting extra pressures in pipe Ill caused by movementof piston 53a to the left under influence of steam pressure delivered through pipe 55. The movement of piston 53a back and forth in cylinder 54a causes slidable member 65 to move on pivot member '66 and slide lengthwise of extension 54 of extending arm 6| thus opening or closing of louvres 4| and 42 depending uponthe directiono'f motion of piston 53a.

Air inlet assemblies I3 and I4 instead ing directly into the smoke boxof the'locomotive as shownin Figure 1 may be connected to'an open bottom air distributing hood 13 (Figure 5) by means of tubular connecting-members Hand. The hood 13 preferably extends slightly below the flared bottom 4 of depending extension 3 of the smoke stack 2. Th'ebottom edge of this hood is alsopreferably beveled slightly inward to aid in directing the fiow of air as wellas products of combustion into the bottom of the Smokestack.

Where the smoke stack is of. round horizontal cross section construction it is normally most convenient to make the hood of similar outline although the invention is not limitedto such shape so long as the principles of the present invensmoke box in manner substantially.preventing any cooling of the smoke. box, This avoids unnecessary stresses and strains on the front tube sheet T E-(Figure 4) superheater headers and units 83, and other highly heated steam containing fparts of the system,aswel1i as all other exposed interior surfaces of the smoke box.

- In preferred construction where the present air inlet system is used for limiting the maximum suction pressure in the locomotive smoke box, the table platelfl, scren l2, and bafile plate ll shown in Figure 2 are -removed,'and diaphragm!) re constructed. An assembly of this nature istypiof openof superheating of the steam can be varied over a considerable-range. Tofacilitate this the area between the diaphragm 9a and front tube sheet 16 1 may be partitioned ofi by means of a substantially U-shaped partition member 84 which in effect boxes in the area of the, front tube sheet 16 which includes the large tubes 82. It is thus obvious that by raising upper damper plate 19 to provide a larger opening for products of combustion through upper screen 11 and choking oif part of the opening through screen 18 with lower damper plate 80, a higher percentage of the hot products of combustion will pass through the upper or superheater portion of the boiler withresultant higher superheat and greater efiiciency based on the Rankin cycle. Any ashes, small cinders,

or dust tending to collectin the bottom of the smoke box at its front end maybe automatically removed and passed out of the'smoke stack by means of suction pipe 85. Modification of diaphragm Set as shown in Figures 4 and 5 makes inspection of the front tube jsheetlfi, tubes ill and 82, and superheater parts easy to accomplish, in contrast with the inspection difiiculties encountered with present standard A. A. R. construction.

Tests of, the presentinvention on. a 4--8-4 I northern type stoker fired. locomotive operatin at various loads shows that twelve inch diameter inlets and disc valves, of the type shown in Fig-' .ure 5, operate exceptionally wall. Air inlet assemblies l3 and I4 in this construction were set at a suction pressure diiferentialof 0.8 ex- '40 pressed in inches of water. The suction pressure with this type of control was reduced in front of the front tube sheet an average of at least 2 inches of water pressure below the average previously maintained with the restricting conventional design bafiles whilewmaintaining ef- 'ficient combustion for all of the requirements 'of the locomotive. This resulted in reduced velocity of the products of combustion through the fire tubes, as well as a marked decreasein fuel consumption. The apparatus was adjusted so that the change from lower maximum to the up per maximum draft occurredwhen the steam ressure to the stoker engine exceeded 30 pounds per square inch gage.

As soon as this rate of fuel feed was exceeded the louvres automatically closed on air inlet assembly l4, whereupon air inlet assembly I3 set for the higher suction pressure went into full operation. Numerous .tests with this system showed that the suction pressures in the front portion ofthe locomotive smoke box could be maintained atsubstantially the same pressures as thosedirectly in' front of the front tube sheet. This produced a more uniform burning fire ,bed, higher efllciency of steam generation, and substantial elimination of smoke due to better and more evencombustion. These improvements and more uniform operating conditions also madepossible the increasing of the internal diameter of theexhaustlstand nozzle inch, i. e. from 8% inches to 8% inches which resulted in an; average reduced back pressure on the driving cylinders; of approximately 6 pounds with greater power efflciency and a :quieter exhaust, and also made possible the increasing of the. grateopening area to one comtion. -This reduced velocity in turn greatly reducedthe loss of unburned and partially burnedcoal through the smoke stack.

- Other modes of applying the principle of my invention may be employed instead of those explained, change being madeas regards the means and steps herein disclosed,provided those stated by any of the following claims or their equivalent-be emp1oyed.- I

-I- therefore particularly claim as my invention:

'1. A method of controlling draft. created in: a steam generator by the flow of a gaseous fluid through a space in the' steam generator wherein suction pressure'is'to-be maintained at a substantially constant predetermined value over a prescribed portion of the operating rangdwhich comprises the steps of introducing in controlled amount a separate suction reducing-gaseous fluid into said space when the suction pressure therein tends to exceed the predeterminedvalue', raising said suction pressure by stopping substantially" the-"whole flow of said suction reducin gaseous fluid.- under conditionswhen same would normally flow into said space,-andagain releaspoint out and distinctly ing the new of suction reducing gaseous fluid.

when control at said substantially constant predetermined value is again tobeutilized.

:2. A method of controlling draftin a steam generator, as set forth in claim- '1', applied to draft regulation' in a locomotive smoke box, in which suction is, created by flowing exhaust steam through said smoke box andout Of a smoke stack connected thereto, which includes the stepsof controlling the upper limit of the suction pressure created by the exhaust steam a-t an intermediate and substantially constant level for low rates or fuel feed by admitting air into the smoke box at said intermediate l'evelto limit the suction pressure approximatelyat that level, while at high rates of fuel feed the upper limit of the suction pressure thus created is raised to a suitably higher substantially constant pressure level by admitting air into-said smoke box at substantially said higher level in variabfe controlled amount sufiicient to limitthe maxi-mum suction pressureapproximately at said predetermined higher level which is; below that to which the suction pressure would otherwise normal-1y rise.

j 3'. In a method of the character described, the stepswhich comprise flowing a gaseous body underpressure through a restricted area iii-manner creating a suction pressure therein, admitting a second gaseous; fluid into said restricted. area when said suction pressure rises to and.- reaches a predetermined level, the amount of said second gaseous fluidadmitted being controlled in manner holding the maximum suction pressurein "said restricted area substantially at said prede' termin'ed pressure level, and changing said predetermined pressure levelto a different pressure level in accordance with change of maximum suction pressure requirements.

4. In combination, a smoke box, means for cre jating'induced draft suction pressure in said smoke box,.and means to automatically limit said suction pressure sothat it does not greatly'exceed apredeterniined level which is below the maximumto' which-it would normally rise, said lastfnamed means oomprising an assembly for admitting a gaseous fluid, such asa'i i intosatd smoke box when the suction pressure therein exsauna ceeds a predetermined level, assembly hairing a housing, avalve seatmember in saids-nous"; ing, a valvemovable to-andfrom said seat,., ar id? means for holding said, valve againstsaidiseat when. the suction pressure in the smoke boxis at least substantially below thepredetermined. level, and-yet permit; same to; leave said seatl and" admit suction reducinggaseous fluid in controlled amount into said smoke box. when the, suction. pressure rises to atleast said-predetermined levelr 5. In combination; with a smoke box and means for creating draft suction pr s e thereini o 6; In combination with a smoke box and means for creating draft suction pressure therein, of valve means adapted to automatically open to admit a suction reducing gaseous fluidfsuclr as air, into said smoke box when thesuction pres.- sure therein reaches a predetermined ;level,,and automatically close when said suction pressure drops below said predetermined level, a. second valve means constructed for operation in like mannerto the first but at a higher predetermined suction pressure level, and means for shifting the suction pressure control fromtheflrst valve means to the second and back in accordance with which predetermined upper suction pressure in the smoke box is chosen to control the admission of suction reducing gaseous fluid, said suction pressure shifting means comprising; pivotally mounted louvres adapted tosubstantially prevent fluid flow through said first. valve. means means for moving said 'separatemeans-alternate- 1y from'wide open-to completely closed :position and back, and means for controlling thetin est movement of said separatermeans from. one of said positionsto theothenp 8.- A railroad locomotive provided with smoke box, a smoke stack connected andextendingia short distance into said smoke box, 1 and means for directing steam into the inner end of-the Smokestack to create asuction; pressure in lsaid smok box, in combinationwitha;hood-around the lower end ofisaid smoke-sta k; sha be- 1 ing open at its bottom and closedatnits top, an open passageway means;connectedtofthe side or said hood to facilitate now of gaseousflfiuid thereinto, and an inletValYe-means adapted to automatically; open ;-to admit Q suction reducing gaseous fluid, such as air, through said o'pe'n'p'assageway means into said hood when the suction mined amount and automatically close when said suction pressure drops below said predetermined amount. v

9. In a methodof controlling suction pressure at least at one predetermined level in a compartment, the steps which comprise creating suction pressure in said compartment, said suction pressure normally rising above said predetermined level if not controlled, admitting a suction reducing gaseous fluid in controlled amount into said compartment when said suction pressure rises to said predetermined pressure level, controlling the flow of said suction reducing gaseous fluid admitted into said compartment so as to hold said suction pressure from rising substantially above said predetermined pressure level, stopping substantially the whole flow of said gaseous fluid when a higher predetermined pressure level is to be maintained in said compartment, and

releasing the whole flow of said gaseous fluid into said compartment when the predetermined lower pressure level is to be again maintained therein.

10. In a method of controlling suction pressure in a compartment, at least at two predetermined levels therein, by means of independently operating inlets thereto for gaseous fluid, the steps which comprise creating suction pressure in said compartment, said suction pressure normally rising above said predetermined levels if not controlled, admitting a suction reducing gaseous fluid into said compartment when, said suction prespressure in said smoke box reaches a predetersure is to be again controlled therein at said lowlocomotives, the combination with a smoke box and means for creating suction pressures therein,

of an air inlet valve adapted to normally openwhen a higher predetermined suction pressure level is to be maintained in said smoke box, a second inlet valve adapted to open and admitair into said smoke box in controlled amount when the suction pressure therein rises to a predetermined higher level and tends to exceed same, and

means for controlling the operation of said means for rendering said first inlet valve inoperative, whereby the suction pressures in said smoke box may be readily shifted from one upper level to another.

12. In combination with a smoke box and means for creating draft suction pressure therein, of valve means adapted to automatically open to admit a suction reducing gaseous fluid, such asair, into said smoke box when the suction pressure therein reaches a predetermined. level, and

automatically close when said suction pressure drops belowsaid predetermined level, means for in said smoke box, and means for controlling the sure has risen to the lowest of said predetermined levels, controlling the amount of said suctionreducing gaseous fluid admitted into said compartment so as to hold said suction pressure from rising substantially above said predetermined lowest level, stopping the flower said gaseous fluid operationyof said means for rendering said inlet valve inoperative, whereby the suction pressures in said smoke box may be readily shifted. from said predetermined suction pressure to a higher admitting a suction reducing gaseous fluid in variable amount into said compartment as soon as said suction pressure reaches the predetermined higher pressure level, controlling the amount of said suction reducing gaseousfiuid admitted to said compartment so as to hold said suction presflow of said gaseous fluid into said compartment at the lower control level when the suction pressuction pressure and back.

13. In, combination with a smoke box and means for creating draft suction pressure therein, of valve means adapted to open and admit a suction reducing gaseous fluid, such as air, into said smoke box when the suction pressure therein reaches one level of a series of predetermined levels, and automatically clos when said suction pressure drops below said level, and means for I completely shifting'from one predetermined level to another of said series, the pressure at which said suction reducing gaseous fluid is admitted to said smoke box.

I ROBERT R. McINTO-SH, 

